Gather your ingredients
Wash the lemons
Zest the lemons
Cut them in half
Squeeze the lemon juice from the lemons
Add water to the bottom half of the double boiler enough to boil but not enough to touch the top pan
Bring it to a boil and reduce to a simmer
Add the eggs to the top pan the one without the water
Whisk together the eggs, zest, lemon juice and sugar in the pot that you are placing on the top half of your double boiler.
Once incorporated well. place on the top of your double boiler
Stir for 8-10 minutes
As the mixture gets warm, add in the cold butter a few small chunks at a time and keep stirring
As it begins to heat it will change in color and texture, pay attention to the sides as the curd will try to cook faster at the edges. Use a rubber spatula to scrap down the sides as you stir.
Once the curd has reached a consistency slight less than the one you are looking for remove from the heat. It will continue to thicken.
Once cool enough to handle, remove the curd from the pot and place into a vessel for refrigerating We use Mason jars but another bowl can work just fine.
If you plan to use the curd same day you will want to get the curd into the freezer, use caution do not place hot glass mason jars in the freezer. If you are placing in the freezer move to freezer safe dishes.